The present invention relates to an optical disk apparatus which can determine, by using an optical pick-up, whether or not an optical disk is loaded therein.
A conventionally used optical disk, such as a CD (compact disk), LD (laser disk) and magneto-optical disk, is loaded in an optical disk apparatus, and the optical disk is clamped by a disk clamper or a stabilizer so as to be rotated therein. Generally, a high grade type optical disk apparatus uses a large size disk clamper or stabilizer because the large size clamper or stabilizer can easily prevent a deflection of rotation of the optical disk.
When operating an optical disk apparatus, an optical disk must be loaded beforehand. Accordingly, in the optical disk apparatus, it is determined whether or not an optical disk has been loaded before starting an operation. One of the methods to determine whether or not an optical disk is loaded is an optically determining method using an existing optical pick-up.
Japanese Laid-Open Patent Application No. 2-289925 discloses a method in which a light beam is radiated from an optical pick-up and a presence of an optical disk is determined by detecting a light beam reflected by the optical disk.
Generally, in optical disk apparatuses, focusing of a light beam is performed by moving an optical pick-up in a direction perpendicular to a surface of the optical disk. If the focusing does not succeed in a predetermined period of time, a focus error signal is generated. Accordingly, when a focusing is performed in a state where an optical disk is not loaded, a focus signal is generated. Japanese Laid-Open Patent Applications No. 62-76061, No. 63-268159 and No. 4-255963 disclose a method in which it is determined whether or not an optical disk is loaded by detecting the above-mentioned focus error signal.
When focusing by means of an optical pick-up, an S-curve detection signal is detected. A zero-cross signal of the S-curve detection signal corresponds to a focused position of the pick-up. Japanese Laid-Open Utility Model Application No. 4-93917 discloses a method in which it is determined that an optical disk is not loaded when the zero-cross signal is not generated. That is, it is determined whether or not an optical disk is loaded by judging a presence of the zero-cross signal at the time when a focussing is performed.
Additionally, other methods are known, in which, for example, a micro switch, which is operated by mechanical means and outputs a detection signal, or a reflection type photo-interrupter is provided to determine whether or not an optical disk is loaded.
However, when determining a presence of an optical disk by detecting the focus error signal by using an optical pick-up, there is a problem in that the determination takes a long time. Additionally, when the optical disk is rotated by means of a large size disk clamper or stabilizer, there is a problem in that an erroneous determination, which is a determination that an optical disk is loaded, may be made despite there being no optical disk loaded, because a light beam is reflected by the clamper or the stabilizer, which condition prevents a generation of the focus error signal.
In the above case, a matting agent may be applied to the disk clamper or stabilizer, or a notch may be provided on a stabilizer at a position facing the pick-up. However, these means need an additional manufacturing process, resulting in a manufacturing cost thereof increasing.
Additionally, in the method in which a micro switch or reflection type photo-interrupter is used, there is a problem in that a manufacturing cost is increased by additional parts to be provided.